Updated at 8:55 p.m. ET: British Prime Minister David Cameron has cancelled a major speech, originally scheduled for Friday, because of the uncertain outcome of the hostage-taking crisis at an Algerian gas plant that started Wednesday, the Telegraph reported.

An unknown number of the hostages — which included dozens of foreign nationals and Algerians — were killed as Algerian forces attempted a rescue mission that reportedly went awry late Thursday. One Briton was reported dead in the hostage crisis, and Cameron warned that the country should be prepared for "further bad news."

Original report:

LONDON — It says a lot about Britain's ambivalent attitude toward its membership of the European Union that the UK Independence Party (UKIP), which wants the country to leave the bloc, has 12 seats in the European Parliament.

Britain is so close to continental Europe — the English Channel is just 26 miles across at its narrowest point — that people sometimes swim to France. But, politically, the country has arguably not been further away for decades.

The right-leaning Telegraph newspaper reported Thursday that "Cameron is expected to pledge to renegotiate Britain’s [EU] membership, if he is re-elected in 2015, after which the revised relationship will be the subject of a referendum."

Reuters described Cameron's looming speech as "one of the most closely watched Europe addresses by a British leader since World War Two."

Political and business leaders have voiced concerns over the risk of calling a referendum that could see Britain leaving the EU, which offers a market of 500 million people on its doorstep.

The EU has been awarded the Nobel Prize for its role in uniting the continent after two World Wars. ITV's James Mates reports.

And Reuters noted that "international partners from the United States to Germany and Ireland have made it clear they oppose a British EU exit and believe that such a move would isolate and damage Britain itself."

Europe's common currency, the euro, is mired in turmoil, leaving most Britons glad the U.K. kept the pound.

John Curtice, electoral analyst and professor of politics at Strathclyde University, said UKIP’s poll surge was a major factor in pushing Britain’s relationship with the rest of Europe to the center of the political agenda.

"There is no doubt that recent electoral success for UKIP has made Europe an issue for Conservatives," he said.

"There is enormous pressure on David Cameron from within his party," he added. "Many Conservative members of parliament are looking ahead to the next election and thinking, 'I'll be damned if I lose because my party cannot come up with a coherent policy on Europe that voters can support.'"

Yves Herman / Reuters, file

The rising star of British politics? UK Independence Party leader Nigel Farage stands near a coffin symbolizing "the death of the Euro" during a demonstration in 2011 urging the European Union to stop extending help to Greece.

Curtice said UKIP’s poll ratings appeared to be driven by mid-term protest votes that traditionally went to Liberal Democrats, but which were up for grabs now that the party has joined the Conservatives in the ruling coalition.

"However, regardless of why UKIP is getting attention, its presence is making Europe a problem for the Conservative party and its supporters, many of whom are instinctively wary of Europe," Curtice added.

One key challenge for Cameron is that getting the EU to change has proved notoriously difficult for successive British prime ministers. Cameron has also often been left isolated at EU summits due to his opposition to various proposals.

Professor Iain Begg, of the European Institute at the London School of Economics, said a hard-line stance by Cameron could potentially result in "amendments to some of the [EU] directives that Britain finds unpalatable."

However, he said that a total renegotiation of the treaties that bind the EU together was unlikely.

Cameron will need to reconcile demands from so-called Euroskeptics within his own party for the repatriation of powers from Brussels with calls from other parts of his coalition government for closer European integration.

And he'll need to do so while not offending his political peers and allies in Europe and beyond.

Speaking to Reuters, one unnamed EU diplomat wondered how Cameron could walk that tightrope:

"Britain's Europe policy has been confusing for a long time. He's going to have to sort out a lot of misunderstandings before he can convince people of what he's doing," said the official, underlining that uncertainty would not go away overnight.

"The risk remains of an exit by mistake. It shouldn't happen, but other things that shouldn't have happened did."

Finland's prime minister signaled he was worried about what Cameron might announce during Friday's speech.

"The EU without Britain is pretty much the same as fish without chips," Jyrki Katainen told reporters in Brussels on Wednesday. "It's not a meal any more."